Much like surface flatness for flat optics, spherical surface power is a measure of the deviation between the surface of the curved optic and a calibrated reference gauge, typically for a 633 nm source, unless otherwise stated. This specification is also commonly referred to as surface fit.

The power density of your beam should be calculated in terms of W/cm. For an explanation of why the linear power density provides the best metric for long pulse and CW sources, please see the Damage Thresholds tab.

The engraving on mounts 1/2" or larger in diameter clearly indicates the part number, focal length, and antireflection coating deposited onto the surface. The engraved arrow indicates the direction of light propagation to collimate a point source, and an infinity symbol denotes that this lens has an infinite conjugate ratio (i.e., if a diverging light source is placed one focal length away from the flat side of the lens, the light rays emerging from the curved side will be collimated). Mounts smaller than Ø1/2" are engraved with the part number only.

These achromatic doublets, which are designed for use in the visible spectral region (400 - 700 nm), are computer optimized at infinite conjugate ratios. The design wavelengths used are the helium "d" (587.6 nm, yellow), hydrogen "F" (486.1 nm, blue/green), and hydrogen "C" (656.3 nm, red) lines since they reasonably represent the visible spectrum and are used to define the Abbe Number, Vd, of a material. For applications in wavelength regimes less than 410 nm, Thorlabs’ air-gap UV doublets provide excellent performance down to 240 nm.

Achromatic doublets are useful for controlling chromatic aberration and are frequently used to achieve a diffraction-limited spot when using a monochromatic source like a laser. Refer to the Application tab above for information about the superior performance of achromatic doublets compared to singlet lenses.

In the specification tables below, a positive radius of curvature indicates that the surface is opening to the right when the lens is oriented as shown in the reference drawing while a negative radius of curvature indicates that the surface is opening to the left. Both the positive and negative lenses have an infinite conjugate ratio (i.e., if a diverging light source is placed one focal length away from the flatter side of the lens, the light rays emerging from the curved side will be collimated).

For best performance, the side of the lens with the largest radius of curvature (flattest side) should face away from the collimated beam. Please see the diagram under the reference drawing link below for details.

Custom Achromatic LensesThorlabs' optics business unit has a wide breadth of manufacturing capabilities that allow us to offer a variety of custom achromatic optics for both OEM sales and low quantity one-off orders. Achromatic optics with customer-defined sizes, focal lengths, substrate materials, cement materials, and coatings are all available as customs. In addition, we can offer optics that exceed the specifications of our stock catalog offerings. To receive more information or inquire about a custom order, please contact Tech Support.

Detailed information regarding each achromatic doublet can be found in the Zemax® files included with the support documents for each doublet. Below are some examples of how the performance of these lenses can be examined using the Zemax®files.

Focal Shift vs. Wavelength

Thorlabs' achromatic doublets are optimized to provide a nearly constant focal length across a broad bandwidth. This is accomplished by utilizing a multi-element design to minimize the chromatic aberration of the lens. Dispersion in the first (positive) element of the doublet is corrected by the second (negative) element, resulting in better broadband performance than spherical singlets or aspheric lenses. The graph below shows the paraxial focal shift as a function of wavelength for the AC508-400-A, which is a 400 mm focal length, Ø50.8 mm achromatic doublet AR coated for the 400 - 700 nm range.

Wavefront Error and Spot Size

Thorlabs' spherical doublet lenses have been corrected for various aberrations, including spherical aberration, chromatic aberration, and coma. One way of displaying the theoretical level of correction is through plots of wavefront error and ray traces to determine spot size. For example, in Figure 2, a plot of the wavefront at the image plane reveals information regarding aberration correction by using the AC254-125-C. In this example, the wavefront error is theoretically on the order of 3/100 of a wave. This indicates that the optical path length difference (OPD) is extremely small for rays going through the center of the lens and at nearly full aperture.

A ray trace for spot size at the image plane of the AC254-250-C is shown below in Figure 3. In this near IR achromatic doublet, the design wavelengths (706.5 nm, 855 nm, and 1015 nm) have each been traced through the lens and are represented by different colors. The circle surrounding the distribution of ray intercepts represents the diameter of the Airy disk. If the spot is within the Airy disk, the lens is typically considered to be diffraction limited. Since the spot size is drawn using geometric ray tracing, spots much smaller than the Airy disk are not achievable due to diffraction.

Understanding Modulation Transfer Function, MTF

MTF image quality is an important characteristic of lenses. A common way to measure this is by using contrast. A plot of the modulation transfer function is used as both a theoretical and experimental description of image quality. The MTF of a lens describes its ability to transfer contrast from an object to an image at various resolution levels. Typically, a resolution target made up of black and white lines at various spacings is imaged and contrast can be measured. Contrast at 100% would consist of perfectly black and white lines. As the contrast diminishes, the distinction between lines begins to blur. A plot of MTF shows the percentage of contrast as the spacing between these lines decreases. The spacing between the lines at the object is usually represented as spatial frequency given in cycles/mm.

The chart shows the theoretical MTF for our Ø25.4 mm, f=200 mm near IR achromatic doublet. The contrast is around 83% at a spatial frequency of about 20 cycles/mm. This represents 83% contrast at0.05 mm spacings between lines. Theoretical MTF shows how well a design can perform if the optic was built exactly to the design dimensions. In reality, most optics fall short of the theoretical due to manufacturing tolerances.

The screen captures to the right and left are actual measurements taken using a USAF 1951 resolution chart as the object.

Achieve a Tighter Focus

The figures below show a comparison of a plano-convex singlet focusing a 633 nm laser beam and an achromatic doublet focusing the same laser beam. The spot (circle of least confusion) from the doublet is 4.2 times smaller than the singlet spot size.

Superior Off Axis Performance

Achromatic doublet lenses have a much reduced sensitivity to centration on the beam axis when compared to spherical singlets and aspheric lenses.

The figures below show two 50.0 mm focal length lenses, one plano-convex and the other an achromatic doublet. Both are Ø25.4 mm lenses with a Ø3 mm beam through the optical axis and one offset by 8.0 mm. Lateral and transverse aberrations are greatly reduced by the achromatic doublet.

Nearly Constant Focal Length Across a Wide Range of Wavelengths

When using a white light source with a singlet lens, the focal point and circle of least confusion are blurred by chromatic aberration. Chromatic aberration is due to the variation of refractive index with respect to wavelength. In an achromatic doublet this effect is somewhat compensated for by using glasses of two different refractive indexes to cancel these aberrations.

The figures below show the effect on focal length for a number of different wavelengths of light through an achromatic doublet and a plano-convex singlet. The figures also shows how the circle of least confusion for white light is reduced by using an achromatic doublet.

Damage Threshold Specifications

Coating Designation(Item # Suffix)

Damage Threshold

-A-ML (Pulsed)

0.5 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.566 mm)

-A-ML (CW)a

1000 W/cm (532 nm, Ø1.000 mm)

The power density of your beam should be calculated in terms of W/cm. For an explanation of why the linear power density provides the best metric for long pulse and CW sources, please see the "Continuous Wave and Long-Pulse Lasers" section below.

Damage Threshold Data for Thorlabs' A-Coated Achromatic Doublets

The specifications to the right are measured data for Thorlabs' A-coated achromatic doublets. Damage threshold specifications are constant for all A-coated achromatic doublets, regardless of the size or focal length of the lens.

Laser Induced Damage Threshold Tutorial

The following is a general overview of how laser induced damage thresholds are measured and how the values may be utilized in determining the appropriateness of an optic for a given application. When choosing optics, it is important to understand the Laser Induced Damage Threshold (LIDT) of the optics being used. The LIDT for an optic greatly depends on the type of laser you are using. Continuous wave (CW) lasers typically cause damage from thermal effects (absorption either in the coating or in the substrate). Pulsed lasers, on the other hand, often strip electrons from the lattice structure of an optic before causing thermal damage. Note that the guideline presented here assumes room temperature operation and optics in new condition (i.e., within scratch-dig spec, surface free of contamination, etc.). Because dust or other particles on the surface of an optic can cause damage at lower thresholds, we recommend keeping surfaces clean and free of debris. For more information on cleaning optics, please see our Optics Cleaning tutorial.

Testing Method

First, a low-power/energy beam is directed to the optic under test. The optic is exposed in 10 locations to this laser beam for 30 seconds (CW) or for a number of pulses (pulse repetition frequency specified). After exposure, the optic is examined by a microscope (~100X magnification) for any visible damage. The number of locations that are damaged at a particular power/energy level is recorded. Next, the power/energy is either increased or decreased and the optic is exposed at 10 new locations. This process is repeated until damage is observed. The damage threshold is then assigned to be the highest power/energy that the optic can withstand without causing damage. A histogram such as that below represents the testing of one BB1-E02 mirror.

According to the test, the damage threshold of the mirror was 2.00 J/cm2 (532 nm, 10 ns pulse, 10 Hz, Ø0.803 mm). Please keep in mind that these tests are performed on clean optics, as dirt and contamination can significantly lower the damage threshold of a component. While the test results are only representative of one coating run, Thorlabs specifies damage threshold values that account for coating variances.

Continuous Wave and Long-Pulse Lasers

When an optic is damaged by a continuous wave (CW) laser, it is usually due to the melting of the surface as a result of absorbing the laser's energy or damage to the optical coating (antireflection) [1]. Pulsed lasers with pulse lengths longer than 1 µs can be treated as CW lasers for LIDT discussions.

When pulse lengths are between 1 ns and 1 µs, laser-induced damage can occur either because of absorption or a dielectric breakdown (therefore, a user must check both CW and pulsed LIDT). Absorption is either due to an intrinsic property of the optic or due to surface irregularities; thus LIDT values are only valid for optics meeting or exceeding the surface quality specifications given by a manufacturer. While many optics can handle high power CW lasers, cemented (e.g., achromatic doublets) or highly absorptive (e.g., ND filters) optics tend to have lower CW damage thresholds. These lower thresholds are due to absorption or scattering in the cement or metal coating.

LIDT in linear power density vs. pulse length and spot size. For long pulses to CW, linear power density becomes a constant with spot size. This graph was obtained from [1].

Pulsed lasers with high pulse repetition frequencies (PRF) may behave similarly to CW beams. Unfortunately, this is highly dependent on factors such as absorption and thermal diffusivity, so there is no reliable method for determining when a high PRF laser will damage an optic due to thermal effects. For beams with a high PRF both the average and peak powers must be compared to the equivalent CW power. Additionally, for highly transparent materials, there is little to no drop in the LIDT with increasing PRF.

In order to use the specified CW damage threshold of an optic, it is necessary to know the following:

Wavelength of your laser

Beam diameter of your beam (1/e2)

Approximate intensity profile of your beam (e.g., Gaussian)

Linear power density of your beam (total power divided by 1/e2 beam diameter)

Thorlabs expresses LIDT for CW lasers as a linear power density measured in W/cm. In this regime, the LIDT given as a linear power density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size, as demonstrated by the graph to the right. Average linear power density can be calculated using the equation below.

The calculation above assumes a uniform beam intensity profile. You must now consider hotspots in the beam or other non-uniform intensity profiles and roughly calculate a maximum power density. For reference, a Gaussian beam typically has a maximum power density that is twice that of the uniform beam (see lower right).

Now compare the maximum power density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately. A good rule of thumb is that the damage threshold has a linear relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 10 W/cm at 1310 nm scales to 5 W/cm at 655 nm):

While this rule of thumb provides a general trend, it is not a quantitative analysis of LIDT vs wavelength. In CW applications, for instance, damage scales more strongly with absorption in the coating and substrate, which does not necessarily scale well with wavelength. While the above procedure provides a good rule of thumb for LIDT values, please contact Tech Support if your wavelength is different from the specified LIDT wavelength. If your power density is less than the adjusted LIDT of the optic, then the optic should work for your application.

Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. The damage analysis will be carried out on a similar optic (customer's optic will not be damaged). Testing may result in additional costs or lead times. Contact Tech Support for more information.

Pulsed Lasers

As previously stated, pulsed lasers typically induce a different type of damage to the optic than CW lasers. Pulsed lasers often do not heat the optic enough to damage it; instead, pulsed lasers produce strong electric fields capable of inducing dielectric breakdown in the material. Unfortunately, it can be very difficult to compare the LIDT specification of an optic to your laser. There are multiple regimes in which a pulsed laser can damage an optic and this is based on the laser's pulse length. The highlighted columns in the table below outline the relevant pulse lengths for our specified LIDT values.

Pulses shorter than 10-9 s cannot be compared to our specified LIDT values with much reliability. In this ultra-short-pulse regime various mechanics, such as multiphoton-avalanche ionization, take over as the predominate damage mechanism [2]. In contrast, pulses between 10-7 s and 10-4 s may cause damage to an optic either because of dielectric breakdown or thermal effects. This means that both CW and pulsed damage thresholds must be compared to the laser beam to determine whether the optic is suitable for your application.

Pulse Duration

t < 10-9 s

10-9 < t < 10-7 s

10-7 < t < 10-4 s

t > 10-4 s

Damage Mechanism

Avalanche Ionization

Dielectric Breakdown

Dielectric Breakdown or Thermal

Thermal

Relevant Damage Specification

No Comparison (See Above)

Pulsed

Pulsed and CW

CW

When comparing an LIDT specified for a pulsed laser to your laser, it is essential to know the following:

LIDT in energy density vs. pulse length and spot size. For short pulses, energy density becomes a constant with spot size. This graph was obtained from [1].

Wavelength of your laser

Energy density of your beam (total energy divided by 1/e2 area)

Pulse length of your laser

Pulse repetition frequency (prf) of your laser

Beam diameter of your laser (1/e2 )

Approximate intensity profile of your beam (e.g., Gaussian)

The energy density of your beam should be calculated in terms of J/cm2. The graph to the right shows why expressing the LIDT as an energy density provides the best metric for short pulse sources. In this regime, the LIDT given as an energy density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size. This calculation assumes a uniform beam intensity profile. You must now adjust this energy density to account for hotspots or other nonuniform intensity profiles and roughly calculate a maximum energy density. For reference a Gaussian beam typically has a maximum energy density that is twice that of the 1/e2 beam.

Now compare the maximum energy density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately [3]. A good rule of thumb is that the damage threshold has an inverse square root relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 1 J/cm2 at 1064 nm scales to 0.7 J/cm2 at 532 nm):

You now have a wavelength-adjusted energy density, which you will use in the following step.

Beam diameter is also important to know when comparing damage thresholds. While the LIDT, when expressed in units of J/cm², scales independently of spot size; large beam sizes are more likely to illuminate a larger number of defects which can lead to greater variances in the LIDT [4]. For data presented here, a <1 mm beam size was used to measure the LIDT. For beams sizes greater than 5 mm, the LIDT (J/cm2) will not scale independently of beam diameter due to the larger size beam exposing more defects.

The pulse length must now be compensated for. The longer the pulse duration, the more energy the optic can handle. For pulse widths between 1 - 100 ns, an approximation is as follows:

Use this formula to calculate the Adjusted LIDT for an optic based on your pulse length. If your maximum energy density is less than this adjusted LIDT maximum energy density, then the optic should be suitable for your application. Keep in mind that this calculation is only used for pulses between 10-9 s and 10-7 s. For pulses between 10-7 s and 10-4 s, the CW LIDT must also be checked before deeming the optic appropriate for your application.

Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. Contact Tech Support for more information.

In order to illustrate the process of determining whether a given laser system will damage an optic, a number of example calculations of laser induced damage threshold are given below. For assistance with performing similar calculations, we provide a spreadsheet calculator that can be downloaded by clicking the button to the right. To use the calculator, enter the specified LIDT value of the optic under consideration and the relevant parameters of your laser system in the green boxes. The spreadsheet will then calculate a linear power density for CW and pulsed systems, as well as an energy density value for pulsed systems. These values are used to calculate adjusted, scaled LIDT values for the optics based on accepted scaling laws. This calculator assumes a Gaussian beam profile, so a correction factor must be introduced for other beam shapes (uniform, etc.). The LIDT scaling laws are determined from empirical relationships; their accuracy is not guaranteed. Remember that absorption by optics or coatings can significantly reduce LIDT in some spectral regions. These LIDT values are not valid for ultrashort pulses less than one nanosecond in duration.

A Gaussian beam profile has about twice the maximum intensity of a uniform beam profile.

CW Laser ExampleSuppose that a CW laser system at 1319 nm produces a 0.5 W Gaussian beam that has a 1/e2 diameter of 10 mm. A naive calculation of the average linear power density of this beam would yield a value of 0.5 W/cm, given by the total power divided by the beam diameter:

However, the maximum power density of a Gaussian beam is about twice the maximum power density of a uniform beam, as shown in the graph to the right. Therefore, a more accurate determination of the maximum linear power density of the system is 1 W/cm.

An AC127-030-C achromatic doublet lens has a specified CW LIDT of 350 W/cm, as tested at 1550 nm. CW damage threshold values typically scale directly with the wavelength of the laser source, so this yields an adjusted LIDT value:

The adjusted LIDT value of 350 W/cm x (1319 nm / 1550 nm) = 298 W/cm is significantly higher than the calculated maximum linear power density of the laser system, so it would be safe to use this doublet lens for this application.

Pulsed Nanosecond Laser Example: Scaling for Different Pulse DurationsSuppose that a pulsed Nd:YAG laser system is frequency tripled to produce a 10 Hz output, consisting of 2 ns output pulses at 355 nm, each with 1 J of energy, in a Gaussian beam with a 1.9 cm beam diameter (1/e2). The average energy density of each pulse is found by dividing the pulse energy by the beam area:

As described above, the maximum energy density of a Gaussian beam is about twice the average energy density. So, the maximum energy density of this beam is ~0.7 J/cm2.

The energy density of the beam can be compared to the LIDT values of 1 J/cm2 and 3.5 J/cm2 for a BB1-E01 broadband dielectric mirror and an NB1-K08 Nd:YAG laser line mirror, respectively. Both of these LIDT values, while measured at 355 nm, were determined with a 10 ns pulsed laser at 10 Hz. Therefore, an adjustment must be applied for the shorter pulse duration of the system under consideration. As described on the previous tab, LIDT values in the nanosecond pulse regime scale with the square root of the laser pulse duration:

This adjustment factor results in LIDT values of 0.45 J/cm2 for the BB1-E01 broadband mirror and 1.6 J/cm2 for the Nd:YAG laser line mirror, which are to be compared with the 0.7 J/cm2 maximum energy density of the beam. While the broadband mirror would likely be damaged by the laser, the more specialized laser line mirror is appropriate for use with this system.

Pulsed Nanosecond Laser Example: Scaling for Different WavelengthsSuppose that a pulsed laser system emits 10 ns pulses at 2.5 Hz, each with 100 mJ of energy at 1064 nm in a 16 mm diameter beam (1/e2) that must be attenuated with a neutral density filter. For a Gaussian output, these specifications result in a maximum energy density of 0.1 J/cm2. The damage threshold of an NDUV10A Ø25 mm, OD 1.0, reflective neutral density filter is 0.05 J/cm2 for 10 ns pulses at 355 nm, while the damage threshold of the similar NE10A absorptive filter is 10 J/cm2 for 10 ns pulses at 532 nm. As described on the previous tab, the LIDT value of an optic scales with the square root of the wavelength in the nanosecond pulse regime:

This scaling gives adjusted LIDT values of 0.08 J/cm2 for the reflective filter and 14 J/cm2 for the absorptive filter. In this case, the absorptive filter is the best choice in order to avoid optical damage.

Pulsed Microsecond Laser ExampleConsider a laser system that produces 1 µs pulses, each containing 150 µJ of energy at a repetition rate of 50 kHz, resulting in a relatively high duty cycle of 5%. This system falls somewhere between the regimes of CW and pulsed laser induced damage, and could potentially damage an optic by mechanisms associated with either regime. As a result, both CW and pulsed LIDT values must be compared to the properties of the laser system to ensure safe operation.

If this relatively long-pulse laser emits a Gaussian 12.7 mm diameter beam (1/e2) at 980 nm, then the resulting output has a linear power density of 5.9 W/cm and an energy density of 1.2 x 10-4 J/cm2 per pulse. This can be compared to the LIDT values for a WPQ10E-980 polymer zero-order quarter-wave plate, which are 5 W/cm for CW radiation at 810 nm and 5 J/cm2 for a 10 ns pulse at 810 nm. As before, the CW LIDT of the optic scales linearly with the laser wavelength, resulting in an adjusted CW value of 6 W/cm at 980 nm. On the other hand, the pulsed LIDT scales with the square root of the laser wavelength and the square root of the pulse duration, resulting in an adjusted value of 55 J/cm2 for a 1 µs pulse at 980 nm. The pulsed LIDT of the optic is significantly greater than the energy density of the laser pulse, so individual pulses will not damage the wave plate. However, the large average linear power density of the laser system may cause thermal damage to the optic, much like a high-power CW beam.

I'm having trouble understanding the lens reference diagram. I need to know the location of the back focal plane of AC508-200-A-MLd relative to the lens, however, on the reference document f, the focal length and f_b, the back focal length are both defined as being in the same direction, and both listed as positive. Yet the back focal plane must be located on the opposite side of the lens to where it is drawn. And the reference plane from which f_b is measured is unclear. Could you clarify from where f_b is measured, and whether it should be measured in the opposite direction to that drawn?

nbayconich
&nbsp(posted 2019-02-06 05:05:29.0)

Thank you for contacting Thorlabs, and I apologize for the confusion. Back-focal length can be an ambiguous term which can refer to two distinct measurements; either the focal length in reverse direction, or (as in this case) the focal distance as measured from the last optical surface along the optical axis. This is the plane from which it is measured in the diagram. The Effective focal length is the focal distance from the principal plane within the optic. The illustration is correct in this case.
These achromats are infinity-corrected, meaning they're designed to have collimated light on one side, and focused or divergent light from the other side. This is why we don't spec a back-focal length as you've described.

busley
&nbsp(posted 2017-08-03 16:30:41.587)

Hello! Is the off-axis and aspheric performance of Ø2" achromatic doublets superior compared to Ø1" optics of the same kind? Thanks for your help.

tfrisch
&nbsp(posted 2017-08-25 04:52:37.0)

Hello, thank you for contacting Thorlabs. It is important to note that these lenses use spherical, not aspheric surfaces. That said, the aberrations will likely be different between a 1" and 2" version of the same focal length as they are not identical even within 1" of the center. There is not a general rule about which will have better performance. I will reach out to you directly to discuss your application.

jale.schneider
&nbsp(posted 2016-12-21 08:51:33.637)

Dear Sir or Madam,
I realized, that I mounted many achromatic doublets in my 4f imaging systems with the wrong orientation. By doublets with a focal lenght >30 mm, I actually could not see any difference in image quality even though they were placed wrongly. However, on Achromats with 7.5 and 10 mm, the wrong orinetation seems to cause severe waverfront distortions. Is it a general fact that the orientation is essential for the short focal lengths and not so essential for the others? Or should I search for another source of wavefront distortion in my setup?
Thank you very much!
Best regards
Jale

tfrisch
&nbsp(posted 2016-12-28 04:02:23.0)

Hello, thank you for contacting Thorlabs. While the question of beam quality requires a full model of the lens to answer, the short version is that these achromatic doublets are designed for infinite conjugate applications, and there is a preferred side for the focus and collimated beam to be on. Spherical and Chromatic aberrations will be most significantly increased in reverse, and the change is expected to be more noticeable for shorter focal lengths. I will reach out to you directly.

ratcliff
&nbsp(posted 2015-09-30 17:06:11.973)

Are the mounted 2-inch lenses mounted in the same kind of lens tubes (SM2L05, SM2M10, etc.) that one would use for an unmounted lens? I am wondering about the outside diameter of the (engraved) tubes used for the mounted lenses. Do they fit properly in the 2-inch tube clamps and slip rings, such as the SM2TC or SM2RC?

jlow
&nbsp(posted 2015-10-01 04:37:23.0)

Response from Jeremy at Thorlabs: The Ø2" mounted lens do have the same outer diameter as the regular SM2 lens tube. They will fit into the SM2RC and SM2TC.

dan.strehle
&nbsp(posted 2014-04-01 12:41:07.26)

Hello, could you please also give front focal length information (eg as front WD) for the use of these lenses in 4f-configurations (I'd be interested in AC254-100 and AC512-150 in particular).
Thanks,
Dan

besembeson
&nbsp(posted 2014-04-03 08:06:16.0)

Response from Bweh E at Thorlabs: We do provide the front and back focal lengths information for these lenses which you can use in a 4f imaging configuration. At the following link (http://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=2696&pn=AC254-100-A-ML#3441), below the section: Ø1" Mounted Achromatic Doublets, AR Coated: 400 - 700 nm, you should see these values with a reference drawing on the right. If you need this information at a particular wavelength, I can get this for you using Zemax.

ulrichschubert
&nbsp(posted 2013-12-19 09:03:42.997)

Where is the Focus (backward/forward) in relation to the edges of the housing?
Thanks!

tcohen
&nbsp(posted 2014-01-02 06:17:01.0)

Response from Tim at Thorlabs: ~68.9mm and ~70.1mm. From the center of the 41.3mm radiused surface to the focal point it is 73.66mm. In the mount there is 4.8mm from the 41.3mm radiused surface to the edge of the housing. Edge of housing to focal point is then ~68.86mm. From the center of the -137.1mm radiused surface to the focal point is 72.89mm. There is 2.8mm from the -137.1mm radiused surface to the end of the external thread. Edge of housing to focal point is then ~70.09mm. Please note there is an engraving which indicates the direction of light to collimate a point source. Although you can use it backward/forward, using in the engraved direction will reduce aberrations by keeping the more curved side towards infinity.

bdada
&nbsp(posted 2012-06-05 19:25:00.0)

Response from Buki at Thorlabs to r.m.dijkstra:
Thank you for participating in our feedback forum. We do not have tested data for CW light but we have some guidelines to provide based on a 1mm diameter beam:
-A coated doublets (4000 - 700nm): 532nm, 100W/cm^2
-B coated doublets (650 - 1050nm): 810nm, 100W/cm^2
-C coated doublets (1050 - 1620nm): 1542nm, 200W/cm^2
Please contact TechSupport@thorlabs.com if you have any questions.

r.m.dijkstra
&nbsp(posted 2012-06-04 09:36:46.0)

Is there also a tested CW damage threshold for these achromat doublets? Or are they only tested with a pulsed source as given by the specs?(532 nm, 10 ns pulse, 10 Hz, Ø0.566 mm)

lmorgus
&nbsp(posted 2012-03-26 10:06:00.0)

A response from Laurie at Thorlabs to Simone.Rupp: Thank you for the comments you left on our website concerning our Mounted Visible Achromatic Doublets. I will email you an excel file that provides the focal length shift data you saw posted in our family image. Additionally, a member of my team is currently working to add this information to the web page. It will be available to a larger group shortly. Thanks again for taking the time to comment and to help us improve the information we provide.

Simone.Rupp
&nbsp(posted 2012-03-26 09:41:14.0)

For other products like achromatic triplets or cylindrical achromatic doublets there are focal length shift data available. But for the Mounted Visible Achromatic Doublets, there's just one example plot for one lens available, without the possibility to download the plot data. It would be very useful for me, possibly also for others, if those plot data (ideally for all the lenses, but at least the data used for the example plot of AC254-100-A) were made available.

sharrell
&nbsp(posted 2011-12-20 10:02:00.0)

Reply from Sean at Thorlabs: Thank you for your feedback on our website presentation! I've added the threading size to all of the product descriptions on this page, and will see that all of our mounted optics descriptions are updated soon.

user
&nbsp(posted 2011-12-20 00:04:11.0)

For the mounted Doublets it would be nice if you could drop the word Achromatic from the descirption and include the thread size on the cell instead. Or use Achromat and drop Doublet, either way freeing up room to include the thread size on the mounting cell.

jjurado
&nbsp(posted 2011-06-02 10:17:00.0)

Response from Javier at Thorlabs to nkaddy: Thank you very much for submitting your request. The AC508-200-A-ML uses a 0.5" long lens tube, and due to the thickness of the lens itself, there is very little usable thread. I would suggest purchasing the unmounted version of this lens (AC508-200-A) and mounting this into a 1" long lens tube (SM2L10). This solution will allow you to easily thread in the SM2 to SM1 adapter(SM2A6).
AC508-200-A:
http://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=120&pn=AC508-200-A#3597.
SM2L10:
http://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=3383&pn=SM2L10#213.
SM2A6:
http://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=1524&pn=SM2A6#3428.

nkaddy
&nbsp(posted 2011-06-02 11:23:11.0)

I need the infinite conjugate face to be coupled into an SM1 tube system. I want to use a 2" optic so I will need a step down SM2 to SM1 coupler but I am concerned that there are no accessible threads on the infinite conjugate face, are there?

user
&nbsp(posted 2010-08-24 18:29:46.0)

A reply from Jens at Thorlabs: looking at the spec tab for the 1" 30mm focal lenght achromat (AC254-030-A1-ML) I see a value of 22.9mm. For the 0.5" version a value of 27.5mm is listed. Is it possible that you looked at the 0.5" version?

tristan.deborde
&nbsp(posted 2010-08-24 14:38:08.0)

Hello, I purchased a pair of the 1" 30 mm focal length achromatic doublets coated for the visible and Im seeing a different value for focal distance from the flat side of the lens than the listed f_b of 27.5 mm. Using a collimated source incident on the curved side, I measure a length of about 23.5 mm from the flat side of the lens to the focal point. Other than the differing focal distance the lenses seem to performing as expected.

Adam
&nbsp(posted 2010-04-28 16:03:56.0)

A response from Adam at Thorlabs to a.heinrici: The infinite conjugate plate is located on the opposite side of the threaded portion of the mount.

a.heinrici
&nbsp(posted 2010-04-28 12:28:16.0)

I have bought such lenses. I did not manage to find out in which direction is the finite and in which the infinite conjugate is